Method for operating a working machine and a working machine

ABSTRACT

A method for operating a working machine provided with a power source providing power and a plurality of power consuming systems connected to the power source includes the steps of providing a model predicting a power demanded by at least one of the power consuming systems, detecting at least one operational parameter indicative of a power demand, using the detected operational parameter in the prediction model, and balancing a provided power to the demanded power according to the prediction model.

BACKGROUND AND SUMMARY

The invention relates to a method for operating a working machine and aworking machine.

The invention is applicable on working machines within the field ofindustrial construction machines, in particular wheel loaders. Thus, theinvention will be described with respect to a wheel loader. However, theinvention is by no means limited to a particular working machine. On thecontrary, the invention may be used in a plurality of heavy workingmachines, e.g. articulated haulers, trucks, bulldozers and excavators.

Wheel loaders are generally provided with an internal combustion engine,a transmission line, a gearbox, driving wheels and a working hydraulicsystem.

The combustion engine provides power to the different functions of thewheel loader. In particular, the combustion engine provides power to thetransmission line and to the working hydraulic system of the wheelloader.

The transmission line transfers torque from the combustion engine to thegearbox, which in turn provides torque to the driving wheels of theloader. In particular, the gearbox provides different gear ratios forvarying the speed of the driving wheels and for changing between forwardand backward driving direction of the wheels.

The working hydraulic system is used for lifting operations and/or forsteering the wheel loader. For this purpose there are at least onehydraulic working cylinder arranged in the wheel loader for lifting andlowering a lifting arm unit, on which a bucket or other type ofattachment or working tool is mounted for example forks. By use ofanother hydraulic working cylinder, the bucket can also be tilted orpivoted. Further hydraulic cylinders known as steering cylinders arearranged to turn the wheel loader by means of relative movement of afront and rear body part of the wheel loader.

To protect the combustion engine of a wheel loader from sudden rapidchanges in the working conditions of the gearbox and the driving wheelsit is common to provide the transmission line with a hydrodynamic torqueconverter or similar arranged between the combustion engine and thegearbox. The hydrodynamic torque converter provides an elasticity thatenables a very quick adaptation of the output torque to the changes inthe working conditions of the gearbox and the driving wheels. Inaddition, a torque converter provides an increased torque duringparticularly heavy working operations, e.g. during acceleration of thewheel loader.

For example, if a wheel loader without the elasticity of a torqueconverter or similar is driven into an obstacle so that the drivingwheels of the vehicle stops this will also stop the combustion engine,since the engine in such designs is rigidly and unyieldingly connectedto the rotation of the driving wheels. However, this will not happen ifa torque converter or similar is arranged between the engine and thedriving wheels or more preferably between the engine and the gear box.On the contrary, if the driving wheels of the wheel loader stops thiscauses the output side (the turbine side) of the torque converter (theturbine side) to stop whereas the input side (the pump side) continuesto rotate together with the engine. The engine will experience a largerinternal resistance from the torque converter but it will not come to astandstill.

However, the elasticity of a hydrodynamic torque converter or similar isnot present between the working hydraulic system and the combustionengine. On the contrary, the combustion engine provides power to thehydraulic pump or pumps of the working hydraulic system in a more orless direct manner, e.g. by means of a mechanical gear wheeltransmission connected between the output shaft of the engine and theinput shaft of the pump or pumps. In other words, a rapid increase ofthe load on the working hydraulic system is transmitted to thecombustion engine without any significant attenuation. Naturally, thismay cause the combustion engine to stall or cause the power provided bythe combustion engine to be fully consumed by the hydraulic systemleaving the transmission line without significant power. This mayprovide an operator of the wheel loader with the highly undesiredimpression that the engine has become to weak to move the wheel loaderin an operable manner. One way of solving the problem of meeting asudden rapid increase of the load on the working hydraulic system is torun the combustion engine of the wheel loader at the higher end of itsspeed range. This provides a power margin which makes it easier for thecombustion engine to meet a rapid load increase on the hydraulic system,e.g. time to recover by increasing the throttle. However, in general ahigher rotational speed leads to significantly increased losses and thusincreased fuel consumption. Therefore, with regard to fuel consumptionit is better to run the combustion engine at lower rotational speeds.

However, this will give a significantly reduced margin for thecombustion engine to recover from sudden rapid increases of the load onthe working hydraulic system.

In addition, to ensure that the hydraulic functions are equally fast atthe lower rotational speeds, i.e. to ensure the same hydraulic flow atthe lower rotational speeds, it is necessary to use larger pumps withhigher displacement. A larger pump displacement requires a larger torquefrom the source driving the pump, i.e. from the combustion engine. Inother words, if we move from higher rotational speeds towards lowerrotational speeds for reducing losses and fuel consumption we will needhydraulic pumps with a higher displacement, which in turn leads to ahigher torque load on the combustion engine. A higher torque load on thecombustion engine at a lower rotational speed implies that the engine isutilized even harder. Hence, compared to the utilization at higherrotational speed for powering hydraulic pumps with a lower displacementit has now become even more difficult for the combustion engine torecover from a rapid increase of the load on the working hydraulicsystem.

Therefore, when designing a modern combustion engine for a workingmachine such as a wheel loader it is desirable to obtain high outputtorques at low rotational speeds and to obtain quick reactions on suddenrapid increase of the load on the working hydraulic system. To this endit is common to employ various turbo chargers or air compressors.However, these and other solutions for reinforcing the performance of acombustion engine are commonly in conflict with increasingly harderemission regulations, particularly with respect to exhaustion gases andvisible smoke emanating from engine responses to sudden rapid increasesof the load on the working hydraulic system. Considering the above thereis clearly a need for a working machine provided with an improved and amore flexible ability to meet a sudden rapid increase of the load on thevarious power requiring and/or torque requiring sub-systems within theworking machine.

It is desirable to provide a method for operating a working machine withan improved and a more flexible ability to balance a sudden rapidincrease of the load on the various power requiring and/or torquerequiring sub-systems within the working machine.

According to an aspect of the present invention, a method is providedfor operating a working machine provided with: a power source providingpower and a plurality of power consuming systems connected to the powersource, characterized by the steps of providing a model predicting apower demanded by at least one of the power consuming systems, detectingat least one operational parameter indicative of a power demand, usingthe detected operational parameter in the prediction model, andbalancing a provided power to the demanded power according to theprediction model. According to a preferred embodiment, the methodcomprises balancing a provided power to the demanded power so that aload on the power source is reduced.

The prediction model may comprise a characteristic representation of theoperative interaction between the power source and the power-consumingsystems, such as a mathematical model in the form of for example anadvanced dynamic simulation model and/or a less sophisticated equationor system of equations.

The inventive method is preferably utilized in a working machine, inwhich different power consuming systems are operated simultaneously,such as in a wheel loader. Especially in such an application, it ispreferable that the method comprises simultaneously monitoring ademanded power of a plurality of the power consuming systems andcorrespondingly balancing the power.

Preferably, the power consuming systems comprises a transmission linearranged between the power source and driving wheels of the workingmachine for transmitting torque from the power source to the drivingwheels. Further, the power consuming systems preferably comprises aworking hydraulic system comprising at least one hydraulic pump poweredby the power source for moving an implement on the working machineand/or for steering the working machine.

According to a preferred embodiment, the method comprises detecting atleast one operational parameter indicative of a current workingcondition of the power source and/or at least one of the power consumingsystems. Detecting the operational parameters for these sub-systems (Ae.the power source, the transmission line and the working hydraulicsystem) creates conditions for providing an earlier indication of thepower balance or the coming power balance in a summation point comparedto detecting the operational parameters for the summation point, inparticularly if the summation point is a fly wheel.

According to a further preferred embodiment, the method comprisesdetecting at least one operational parameter by detecting at least oneinput command from a working machine operator. Detecting the commandsgiven to the sub-systems provides an even earlier indication of thepower balance or the coming power balance in the summation point.Further, by detecting the operator commands, an accurate prediction ofthe behaviour of the power source and the power consuming systems may beperformed.

Preferably, the method comprises both detection of at least oneoperational parameter indicative of a current working condition of thepower source and/or at least one of the power consuming systems and atleast one input command from a working machine operator.

According to a further preferred embodiment of the inventive method, thepower consuming systems are connected to the power source via abranching-off portion, and that the prediction model comprises a powersummation point, which represents the branching off portion. Thus, thesummation point in the prediction model corresponds to a physical pointwhere the power from the power source is divided to the different powerconsuming systems. In other words, the predicted power to the powerconsuming systems are subtracted from a predicted power delivered fromthe power source according to the prediction model. The methodpreferably comprises balancing the power when the prediction modelindicates that the power communicated between the power source and thepower consuming systems is or will be below zero in the summation point.Further, the method preferably comprises the step of temporarilyadjusting the balance until the prediction model indicates a balancecondition in which said power is zero or above zero in the summationpoint.

Said power balancing may be performed in a plurality of alternativeand/or contributory ways, such as by adding torque to the transmissionline by means of an external power source (such as an electric machine),by effecting the power source and/or at least one of the power consumingsystems, and by reducing (such as by scaling down) an actual powerprovided to at least one of the power consuming systems relative to ademanded power.

Utilizing an external power source is particularly advantageous sincethis reduces the need for decreasing the performance of the powerrequiring sub-systems and/or torque requiring sub-systems within theworking machine. In addition, the demands on the main power source ofthe working machine can be relaxed.

The use of at least one electric machine is advantageous, since thisenables a flexible and compact design. An electric machine can also bepowered by means of a plurality of power sources (e.g. batteries,generators, fuel cells etc), which provides an increased freedom in thedesign. Moreover, electric machines react fast on commands and theyprovide a large torque already at low rotational speeds, which isbeneficial considering that a rather large torque may have to besupplied fairly fast.

It is preferred that the electric machine is arranged upstream apossible transmission unit arranged in the transmission line, orupstream a possible gearbox arranged in the transmission line. In thisway the electric machine does not have to work in both clockwise andcounter clockwise directions to accommodate for both a forward and areverse driving selected by means of the gear box. Moreover, arrangingthe electric machine upstream the transmission unit enables a moredirect torque support to branching-off portion, which in most cases isphysically positioned at a point that is located upstream a possibletransmission unit.

It is also desirable to provide a working machine with an improved and amore flexible ability to balance a sudden rapid increase of the load onthe various power requiring and/or torque requiring sub-systems withinthe working machine. According to an aspect of the present invention, aworking machine is provided with: a power source adapted to providepower and a plurality of power consuming systems connected to the powersource, characterized by a control unit which is adapted to predict apower demanded by at least one of the power consuming systems on thebasis of at least one operational parameter indicative of a powerdemand, means for detecting said at least one operational parameter,wherein the detection means is connected to the control unit, and meansfor balancing a provided power to the demanded power according to theprediction model, wherein said balancing means is connected to thecontrol unit.

The working machine displays the same or similar advantages as themethod described above.

Further advantages and advantageous features of the invention aredisclosed in the following description.

Definitions

The term “electric machine” should be understood as a term for anelectric motor and/or generator. The electric machine can be driven byelectricity to supply an output torque to a shaft or be mechanicallydriven by receiving torque on a shaft for producing electricity.

The term “transmission unit” comprises hydraulic clutches, bothhydrodynamic clutches such as torque converters and hydrostaticclutches, as well as mechanical clutches. Thus, “transmission unit”comprises both torque converters which can increase the torque andordinary skid clutches without ability to increase the torque.

The term “driving wheels” is meant to comprise vehicle wheels for directengagement with the ground as well as vehicle wheels for driving aground engaging member, such as tracks, crawlers or similar.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed description of the present invention is given below withreference to a plurality of exemplifying embodiments as illustrated inthe appended figures, in which:

FIG. 1 is a lateral view illustrating a wheel loader having a bucket forloading operations, and a working hydraulic system for operating thebucket and steering the wheel loader,

FIG. 2 is a schematic illustration of a working hydraulic system for awheel loader,

FIG. 3 is a schematic illustration of La. a transmission line of a wheelloader according to an embodiment of the present invention,

FIG. 4 is a schematic block diagram which schematically illustrates thepower exchange between the units of a wheel loader as illustrated inFIG. 3.

FIG. 5 is a diagram which schematically illustrates the torque producedat different rotation speeds for an exemplifying combustion engine.

FIG. 6 is a schematic illustration of La. a transmission line of a wheelloader according to another embodiment of the present invention,

FIG. 7 is a schematic block diagram which illustrates the power exchangebetween the units of a wheel loader as illustrated in FIG. 6.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Structureof Preferred Embodiments

A Working Machine

FIG. 1 is an illustration of an exemplifying working machine in the formof a wheel loader 1 having an implement 2 in the form of a bucket 3. Thebucket 3 is arranged on an arm unit 4 for lifting and lowering thebucket 3. The bucket 3 can also be tilted or pivoted relative to the armunit 4. For this purpose the wheel loader 1 is provided with a workinghydraulic system 140 comprising at least one hydraulic pump (not shownin FIG. 1) and working cylinders 5 a, 5 b, 6 for lifting and lowering ofthe arm unit 4, and for tilting or pivoting the bucket 3. In addition,the working hydraulic system comprises working cylinders 7 a, 7 b forturning the wheel loader 1 by means of relative movement of a front body8 and a rear body 9. These features of the wheel loader 1 and variationsthereof are well known to those skilled in the art and they need nofurther explanation.

A Hydraulic System

FIG. 2 is a schematic illustration of an exemplifying working hydraulicsystem 140. The embodiment illustrated in FIG. 2 comprises two workingcylinders known as lifting cylinders 5 a, 5 b. The lifting cylinders 5a, 5 b are arranged for lifting and lowering the arm unit 4. A furtherworking cylinder known as tilting cylinder 6 is arranged for tilting-inor tilting-out the bucket 3 relative to the arm unit 4. In addition, twoworking cylinders known as the steering cylinders 7 a, 7 b are arrangedfor steering the wheel loader 1. Three hydraulic pumps 142, 144, 146supply the hydraulic cylinders with hydraulic oil. More specifically, aseparate pump is provided for supplying oil to the hydraulic cylinder(s)of each function (lifting, tilting, steering) via a separate circuit. Anoperator of the wheel loader 1 can control the working cylinders bymeans of instruments connected to a control unit (not shown). Preferablythe cylinders 5 a, 5 b, 6, 7 a and 7 b schematically illustrated in FIG.2 correspond the cylinders 5 a, 5 b, 6, 7 a and 7 b shown in FIG. 1.

A Transmission Line

FIG. 3 is a schematic illustration of i.a. a transmission line 110 of awheel loader 1 according to an embodiment of the present invention. Apower source in the form of an internal combustion engine 120 isarranged at one end of the transmission line 110 and the driving wheels130 of the wheel loader 1 are arranged at the other end of thetransmission line 110. In other words, the internal combustion engine120 is arranged to supply torque to the driving wheels 130 via thetransmission line 110. Preferably the transmission line 110 comprises agearbox 118 for varying the speed of the driving wheels 130 of the wheelloader 1 and for changing between forward and backward driving directionof the wheels 130. The gearbox 118 may e.g. be an automatic gearboximplying that there must not necessarily be a clutch (not shown) betweenthe gearbox 118 and the driving wheels 130, which is common in case of amanual gearbox.

The transmission line 110 is further provided with a transmission unit114 for reducing the mechanical interaction between the internalcombustion engine 120 and the driving wheels 130, i.e. for providingslipping or skidding or even for temporarily disengaging the combustionengine 120 from the driving wheels 130. The main purpose is to protectthe engine 120 from sudden rapid changes in the working conditions ofthe gearbox 118 and the driving wheels 130. The transmission unit 114 ispreferably a hydraulic clutch of the type called hydrodynamic torqueconverter. As is well known, a torque converter is 5 adapted to increasethe input torque applied to the converter. The output torque can be inthe interval of e.g. 1-3 times the input torque. The torque convertermay also have a free wheel function and/or a lock-up function providinga direct operation without any increased torque. In case of a lock-upfunction it is preferred that the lock-up state provides a fixedtransmission ratio of substantially 1:1. Naturally, other types oftransmission units are conceivable for providing a reduced mechanicalinteraction between the combustion engine 120 and the driving wheels130, e.g. a skid clutch without any torque-increasing ability. The exactposition of the transmission unit 114 within the transmission line 110is not decisive. However, it is preferred that the transmission unit 114is positioned after (i.e. downstream) the combustion engine 120 andbefore (i.e. upstream) the gearbox 118.

In addition, the transmission line 110 is provided with a powertransferring unit 116 for driving the hydraulic pumps 142, 144, 146 ofthe hydraulic system 140 to enable the lifting, tilting and steeringoperations mentioned above. The power transferring unit 116 may e.g. begear wheels or some other suitable power transferring means arranged tointeract with the transmission line 110 for transferring power from thecombustion engine 120 to the hydraulic pumps 142, 144, 146. The powertransferring means 116 is preferably arranged to interact with thetransmission line 110 in a position upstream the gear box 118 and morepreferably in a position between the internal combustion engine 120 andthe transmission unit 114. In other words, the power transferring unit116 forms a branching-off portion for the division of the power from thepower source 120 to the power consuming systems in the form of thetransmission line 110 and the hydraulic system 140.

It should be added that the combustion engine 120 can be replaced byother power sources, e.g. a power source in the form of a gas turbine oreven a fuel cell arrangement.

In addition, the transmission line 110 may be fully or at least partlyreplaced by a hydraulic transmission or an electric transmission. Anelectric transmission may e.g. be implemented by means of cables orsimilar that supplies power from an electric power source to one orseveral electric motors for operatively propelling the driving wheels130. Likewise, the power transferring unit 116 may be fully or at leastpartly replaced by another power transferring unit based on hydraulic orelectric principles. For example, the hydraulic pumps 142, 144, 146 maybe powered by means of electric motors receiving power from thecombustion engine 120 via a generator arrangement or similar.

Power Exchange and a Torque-Control Unit

The attention is now directed to FIG. 4, which is a schematic blockdiagram of the power exchange between the transmission line 110, theinternal combustion engine 120 and the working hydraulic system 140 ofthe wheel loader 1 as previously described with 10 reference to FIG.1-3. The transmission line 110 is at least connected to the drivingwheels 130 of the wheel loader whereas the working hydraulic system 140is at least connected to an implement 2.

As can be seen in FIG. 4 the transmission line 110, the internalcombustion engine 120 15 and the hydraulic system 140 are connected to atorque-control unit 200 or a similar control unit being arranged tooperatively control the power/torque exchanged between the transmissionline 110, the internal combustion engine 120 and the hydraulic system140. The torque-control unit 200 is preferably implemented as one orseveral hardware units arranged at one or several locations within thewheel loader 1 and provided with the appropriate circuitry and softwareneeded to accomplish the required functions, e.g. circuitry forprocessing and storing; and software for executing and controlling anyrequired processing and storing. In particular, it is preferred that thetorque-control unit 200 is provided with substantial processingcapabilities and advanced functions for controlling the power/torqueexchanged between the transmission line 110, the internal combustionengine 120 and the hydraulic system 140 depending on algorithms orsimilar working on data received from control units and/or sensors orsimilar arranged within the wheel loader 1.

It is preferred that the torque-control unit 200 is connected to thesub-units 110, 120, 140 by means of a CAN-bus or possibly to aMOST-network or any other communication means that is used forconnecting various units within the wheel loader 1. This isschematically illustrated in FIG. 4 by means of dashed lines connectingthe sub-units 110, 120, 140. In fact, the torque-control unit 200 ispreferably connected to the sub-units 110, 120, 140 via control-unitsand/or sensors or similar being arranged in the sub-units 110, 120, 140for operatively monitoring the operation of the same.

Hence, the torque-control unit 200 is preferably connected to thecombustion engine 120 5 by means of an engine ECU 129 (ElectronicControl Unit, ECU) or similar. There are a wide variety of well knownengine ECUs that are frequently used by those skilled in the art forcontrolling combustion engines, e.g. for monitoring and controlling suchparameters as the torque and rotational speed provided by the engine.These well known ECUs need no further description.

Similarly, the torque-control unit 200 is preferably connected to thetransmission line 110 by means of a transmission line ECU 119 forcontrolling for example the gear box 118. The ECU 119 is connected tosensors or similar being arranged for monitoring and controlling theoperation of the transmission line 110. The sensors may e.g. be sensorsfor measuring torque and rotational speed in connection with thetransmission line 110. The transmission line ECU 119 may also compriseor be connected to a brake ECU, e.g. in the form of an ECU for an ABS(Anti-Locking Brake System, ABS).

Likewise, the torque-control unit 200 is preferably connected to thehydraulic system 140 20 by means of a hydraulic system ECU 149 thatcomprises or is connected to sensors or similar being arranged formonitoring and controlling the operation of the hydraulic system 140.The sensors may e.g. be sensors for measuring the hydraulic pressure andflow provided by the hydraulic pumps 142, 144, 146 in the hydraulicsystem 140. Utilizing information from ECUs and/or sensors as mentionedabove enables the torque control-unit 200 to monitor the current workingcondition of the sub-units 110, 120, 140 in the wheel loader 1 as willbe discussed in more detail later.

In addition (or alternatively), instruments 220 for controlling thesub-systems 110, 120, 30 140 are typically arranged in the drivingcompartment of the wheel loader 1. The instruments are preferablyconnected to the torque-control unit 200 via a CAN-bus or possibly to aMOST-network or any other suitable communication means. This enables thetorque-control unit 200 to monitor the commands given from theinstruments to the sub-systems 110, 120, 140 and manipulate the signals.35 The instruments 220 can e.g. be one or several joy-sticks or similarfor controlling the hydraulic pumps 142 and 144 coupled to the liftingand tilting cylinders 5 a, 5 b and 6 as described above. The instrument220 can also be a steering wheel or similar for controlling the pump 146coupled to the steering cylinders 7 a and 7 b as described above. Inaddition, the instruments 220 may be a gas pedal for controlling thecombustion engine 120 or a brake pedal for controlling the brakingaction of the wheel loader 1. Naturally, other instruments forcontrolling the sub-systems 110, 120, 140 are clearly conceivable.

Commands from the instruments 220 are preferably transferred to ECUs orsimilar being arranged to control the sub-systems 110, 120, 140. Asindicated above, it is preferred that the commands are transferred via aCAN-bus or a MOST-network or any other suitable communication means towhich the torque-control unit 200 is connected. For example, commandsfrom a brake pedal to a brake ECU (e.g. an ABS Anti-Locking BrakeSystem, ABS) affects the brakes acting on the driving wheels 130 of theof the wheel loader 1, which in turn affects the transmission line 110.Similarly, commands from a gas pedal to an engine ECU may affect fuelinjecting and turbo charging systems, which in turn affects thecombustion engine 120. Commands from a joy-stick or a steering wheel orsimilar to a hydraulic ECU may affect the hydraulic pumps 142, 144, 148and/or possible valves in the hydraulic system 140, which in turnaffects the hydraulic system 140 as a whole.

Knowing the current working condition of the sub-systems 110, 120, 140and/or the commands given to the sub-systems 110, 120, 140 makes itpossible to predict the change in the working condition for thesub-system 110, 120, 140, provided that the characteristic of thesub-systems 110, 120, 140 are known. Hence, it is preferred that thetorque-control unit 200 is provided with suitable information about thecharacteristics of the transmission line 110, the internal combustionengine 120 and the hydraulic system 140. A prediction model is providedcomprising characteristics in the form of implicit or explicit equationsor look-up tables or any other theoretical or empirical obtainedrepresentation. This will be described in more detail later.

Power Exchange and a Summation Point

The schematic block diagram in FIG. 4 shows a summation point 150 towhich the transmission line 110, the internal combustion engine 120 andthe hydraulic system 140 of the wheel loader 1 are schematicallyconnected. The summation point 150 represents the branching-off portion116 between the engine 120 and the transmission line 110 and thehydraulic system 140. The branching-off portion is according to oneexample a mechanical flywheel to which the sub-systems 110, 5 120, 140are mechanically coupled. This is illustrated in FIG. 4 by means ofsolid lines connecting the sub-systems 110, 120, 140. The summationpoint 150 is created or represented by calculations and/or estimationsor similar performed by the torque-control unit 200 based onmeasurements or similar received from sensors and/or ECUs or similarbeing connected to or arranged in the sub-systems 110, 120 140.

In fact, almost every working machine comprises various torque providersand torque consumers that have to be balanced. The summation point 150that is shown in FIG. 4 is such a point wherein torque providers andtorque consumers of the wheel loader 1 can be advantageously balanced.

As long as the sub-systems 110, 120 140 are operating under staticconditions the sum of the powers/torques added to and subtracted fromthe summation point 150 are equal to zero. A sum above zero results inan increased rotational speed for the combustion engine 120 and a sumbelow zero results in a reduced rotational speed for the engine 120.

The powers added and subtracted to and from the summation point 150 canillustrated by the following relation:

P=T−ω  (1)

wherein

-   P is the power (W)-   T is the torque (Nm)-   ω is the angular speed (rad/s)

As is well known, the angular speed ω (rad/s) correspond to therotational speed n (rpm) multiplied by a constant. The powers/torqueswith respect to the sub-systems 110, 120, 140 in FIG. 4 are representedby torques and rotational speeds as follows:

-   Te is the torque currently provided by the combustion engine 120,-   ne is the rotational currently speed provided by the combustion    engine 120,-   Th is the torque currently required by the working hydraulic system    140,-   nh is the rotational speed currently required by the working    hydraulic system 140,-   Tt is the torque currently required by the transmission line 110,-   nt is the rotational speed currently required by the transmission    line 110.

The most common case is probably a summation point 150 representing amechanical flywheel or similar to which the sub-systems 110, 120, 140are mechanically coupled. Here the rotational speeds for the differentsub-systems 110, 120, 140 have a fixed relationship with respect to eachother. The sub-systems 110, 120, 140 may even have the same rotationalspeed n. Hence, during operation under static conditions in this casethe sum of all torques added to and subtracted from the summation point150 is equal to zero. A sum above zero results in an increasedrotational speed for the combustion engine 120 and a sum below zeroresults in a reduced rotational speed for the engine 120.

Function of Preferred Embodiments

Above we have discussed the structure of preferred embodimentsimplemented in a working machine in the form of an exemplifying wheelloader 1. The exemplifying wheel loader 1 comprises La. a transmissionline 110, an internal combustion engine 120 and a working hydraulicsystem 140.

By monitoring the current working conditions for the sub-systems 110,120, 140 and by monitoring the commands given to the sub-systems 110,120, 140 it is possible to predict any change in the current workingconditions, provided that the characteristics of the subsystems areknown. This will be described in more detail below. Monitoring theCurrent Working Conditions

The current working condition for the transmission line 110 can beobtained by e.g. measuring the torque Tt and the rotational speed ntmentioned above with reference to FIG. 4.

This can be accomplished by means of torque sensors and sensors formeasuring rotational speed or similar. However, in an alternativeembodiment at least some of the variables needed to obtain the currentworking condition for the transmission line 110 may be estimated and/orcalculated based on knowledge about the current operation of unitscomprised by the transmission line 110, e.g. the current operation ofthe transmission unit 114.

The current working condition for the combustion engine 120 can beobtained by e.g. measuring the torque Te and the rotational speed nementioned above with reference to FIG. 4. However, in an alternativeembodiment at least some of the variables needed to 15 obtain thecurrent working condition for the engine 120 may be estimated and/orcalculated based on knowledge about the current operation of the fuelinjection arrangement and/or the turbo charger of the combustion engine120 etc. Such knowledge can typically be obtained from the engine ECU129 mentioned above. The current working condition for the workinghydraulic system 140 can be obtained by e.g. measuring the torque Th andthe rotational speed np mentioned above with reference to FIG. 4. It isthen assumed that the transmission line 110 is provided with arotational power transferring means 116 for driving the hydraulic pumps142, 144, 146 of the hydraulic system 140 or at least that the hydraulicpumps 142, 144, 146 are provided with rotational shafts or similarhaving torques and rotational speeds that can be measured. However, ifthis is not so the current working condition for the hydraulic system140 can be alternatively obtained by e.g. measuring the hydraulicpressure and flow provided by the hydraulic pumps 142, 144, 146. Thisfollows from the fact that the power produced by an ordinary hydraulicpump is closely related to the pressure and flow produced by that pump.In addition, the working condition for the hydraulic system 140 may beobtained by measuring the pressure and rotational speed for the pumps142, 144, 146 and estimating the flow or displacement for the pumps 142,144, 146. However, in an alternative embodiment at least some of thevariables needed to obtain the current working condition for the workinghydraulic system 140 may be calculated and/or estimated.

Monitoring the Commands

A command from an operator to an ordinary mechanical system such as thesub-systems 110, 120, 140 is always executed with some delay. The delaymay e.g. be caused by the 5 transmission of the command, by theexecution of the command through mechanical parts and other units in thesub-system and by the natural inertia and similar in the sub-systemsetc. Hence, by monitoring the commands from an operator of the wheelloader 140 to the sub-systems 110, 120, 140 it is possible to predict afuture working condition for the subsystems 110, 120, 140 before it canbe actually measured by sensors in the sub-system 10 110, 120, 140. Thecommands now discussed are typically given by an operator of the wheelloader 1 utilizing various instruments arranged in the drivingcompartment of the wheel loader 1 as discussed above.

The Characteristics of the Sub-Systems—Predicting Working Conditions

We have now discussed the monitoring of the current working conditionsfor the subsystems 110, 120, 140 and the monitoring of the commandsgiven to the sub-systems 110, 120, 140. To be able to predict any changein the current working conditions we will also need the characteristicsof the sub-systems 110, 120, 140. This will be discussed in more detailbelow.

The characteristics of the combustion engine 120 can e.g. be representedby the torque and the rotational speed produced by the engine 120. Thisis illustrated in FIG. 5 showing a diagram with a graph thatschematically illustrates the torque Te (Nm) produced at differentrotational speeds ne (rpm). The torque Te and the rotational speed necorrespond to the maximum available output power Pe from the combustionengine 120 at that particular rotational speed ne according to thegeneral and well known relation P−T ω as given in relation (1) above,wherein the angular speed ω (rad/s) is the same as rotations per minute(rpm) multiplied by a constant.

For example, an operator of the wheel loader 1 may run the engine 120 ata rotational speed of nx (rpm) giving a maximum available output torqueof Tx (Nm) and a currently available maximum output power Pe- However,the current load Pioad <on> the engine 120 may only be a fraction of themaximum available output power Pe. i.e. the engine 120 is only providingthe fraction Pload of the maximum output power Pe to the sub-systems 110and 140. Naturally, the power Poad at the rotational speed nx (rpm)corresponds to a torque TOad that is provided by the engine 120. Thisenables the engine 120 to respond to an increased load within a loadmargin of Pdiff=Pe−Pload without having to increase 5 the rotationalspeed x (rpm). In other words, this enables the engine 120 to respond toan increased load within a load margin of Tdiff=Tx −Toad without havingto increase the rotational speed nx (rpm) as illustrated in FIG. 5. Ifmore power and torque is required this can be provided by increasing therotational speed ne of the combustion engine 120. However, this can onlybe successfully done up to the maximum torque at the top of the graph inFIG. 5 after which the output torque from the combustion engine 120declines. Usually an engine's maximum torque and maximum power can notbe found at the same rotational speed. For most engines the rotationalspeed for maximum power output lies higher than the rotational speed formaximum torque. That means that even after the peak and subsequentdecline of engine torque the engine power still increases until it peaksand thereafter declines, too.

From the above it follows that by monitoring the commands to thecombustion engine 120 (i.e. typically the commands from a gas pedal tothe engine ECU 129), which commands e.g. comprise the rotational speedne or similar to be produced by the combustion engine 120, it will bepossible to predict the maximum torque Te,pred and maximum power.Pe.pred that will be available from the engine 120 in the next instant.It should be added that the commands to the combustion engine (i.e.typically the commands from a gas pedal to the engine ECU 129) mayalternatively comprise the torque Te or power Pe to be produced by thecombustion engine 120.

The attention is now directed to the characteristic of the hydraulicsystem 140. This characteristic can e.g. be represented by the pressuresand flows that are produced by the hydraulic pumps in the hydraulicsystem 140 at different rotational speeds. For an ordinary hydraulicpump this can e.g. be described by the following relations:

tP=PpDp/(2πηhm)  (2)

Dp=Qp/(npηvol)  (3)

Pp=Tp·np  (4)

wherein

-   Tp represents the input torque required by the pump-   Pp represents the pressure generated by the pump-   Dp represents the displacement generated by the pump-   ηhm represents the hydromechanical efficiency-   Qp represents the flow generated by the pump-   np represents the rotational speed for the pump-   ηvol represents the volumetric efficiency-   Pp represents the power required by the pump

It follows that an increased load on the hydraulic system 140 comprisingthe pumps 142, 144, 148 will require an increased pressure pp and/orthat an increased flow demand will require an increased displacement Dpfor at least one of the pumps 142, 144, 148. Both in turn require anincreased input torque Tp to the pump in question and/or an increasedrotational speed ηp, i.e. an increased input power Pp. Thehydromechanical efficiency ηhm and the volumetric efficiency ηvol forthe pump in question are mainly dependent on pressure, rotational speedand displacement (but also on oil viscosity, temperature etc) and theycan e.g. be represented by a look-up table stored in the torque-controlunit 200.

Hence, by monitoring the commands to the pumps 142, 144, 148, whichcommands directly or indirectly comprise e.g. at least one of thevariables pressure pp, displacement Dp or flow Qp to be produced by thepump in question, it will be possible to predict the power Ph.predand/or the torque Tn,pred required by the hydraulic system 140. It willalso be possible to predict the rotational speed ηh,pred required by thehydraulic system 140 in case the transmission line 110 is provided witha rotational power transferring means 116 or similar for driving thehydraulic pumps 142, 144, 146.

The attention is now directed to the characteristic of the transmissionline 110. This characteristic can e.g. be represented by thecharacteristic of the transmission unit 114 arranged therein. Anexemplifying table representing the characteristics of the transmissionunit 114 may e.g. comprise the following variables:

-   Tin represents the input torque to the transmission unit-   nin represents the input rotational speed to the transmission unit-   Tout represents the output torque from the transmission unit-   nout represents the output rotational speed from the transmission    unit

This illustrates that a certain torque Tin and a certain rotationalspeed njn being inputted to the transmission unit 114 correspond to acertain torque Tout and a certain rotational speed nout being outputtedfrom the soft transmission unit 114. Such a table can comprise allrelevant load cases for a certain transmission unit, e.g. measured inlaboratory conditions and/or sampled in real life use.

Alternatively or additionally, the characteristic of the transmissionunit 114 can be represented by means of one or several mathematicalexpressions or similar. For example, a simplified model is given by thetwo mathematical relations below. The model is commonly used to describethe characteristic of a transmission unit in the form of a hydrodynamictorque converter. Naturally, depending on the nature of the transmissionunit there are clearly other mathematical relations or expressions orsimilar that can be used to describe the characteristic of a particulartransmission unit.

The simplified model mentioned above is based on two simple relations.

Tin=k(v)n ² _(in) , where k(v)=T _(in,ref)(v)  (6)

n² _(in,ref)

T _(out)=μ(v)T _(in)  (7)

wherein

-   Tin represents the input torque-   Tin,ref represents the input torque at a determined reference input    rotational speed-   Tout represents the available output torque-   nin represents the input rotational speed-   nin.ref represents a determined reference input rotational speed-   k(v) represents the absorption factor for the converter in question    at different input and output rotational speeds-   μ(v) represents the amplifying factor for the converter in question    at different input and output rotational speeds-   v represents the input rotational speed njn divided by the output    rotational speed nout

Values for the factors k(v) and μ(v) with respect to a certain torqueconverter can be obtained by running the converter at a reference inputrotational speed nin,ref (e.g. at 1000 rpm) while the output rotationalspeed is varied. The simplified converter model described by therelations 6, 7 above and the manner of obtaining the factors k(v) andμ(v) are well known to those skilled in the art and they need no furtherexplanation.

It follows that in case the transmission unit 114 is implemented as ahydrodynamic torque converter it is possible to calculate the availableoutput torque Tout from the transmission unit 114 by measuring the inputrotational speed njn and by knowing the two factors k(v) and μ(v).Naturally, the same or similar can be accomplished for a generaltransmission unit 114 by means of searching in a look-up tabledescribing the characteristic of the transmission unit 114 as mentionedabove.

Now, by monitoring the commands to units and systems that affect theworking condition of the transmission line 110 it will be possible topredict the output torque and the output rotational speed that will berequired from the transmission unit 114 in the next instant. Using thecharacteristic for the transmission unit 114 as describe above it isthen possible to predict the torque Tpred and the rotational speednt,pred that will be required by the transmission unit 114 and thetransmission line 110 from the combustion engine 120 in the nextinstant, i.e. it will be possible to predict the power Pt.pred that willbe required from the combustion engine 120 in the next instant.

In particular it is preferred to monitoring the commands from a brakepedal to a brake ECU (e.g. to an Anti-Locking Brake System, ABS), whichcommands comprise the magnitude of the braking torque or similar to beimposed on the driving wheels 130 and hence on the transmission line110. However, the torque-control unit 200 may need a look-up table orsimilar for converting the command to the brake ECU so that the commandcorresponds to the torque or similar that will be imposed on thetransmission line 110 in the next instant. Such a table can e.g. beobtained by empiric tests in laboratory environments or by measurementsduring real-life driving or similar.

Response to a Rapid Increase of the Load on the Sub-Systems

Above we have discussed the current working conditions for thesub-systems 110, 120, 140 and the commands given to the sub-systems 110,120, 140. We have also discussed the prediction of any change in theworking conditions based on the current working conditions, themonitored commands and the characteristics of the sub-systems 110, 120,140.

As will be discussed in more detail below, a prediction with respect tothe summation point 150 makes it possible to balance torque providersand torque consumers to meet a sudden rapid increase of the load on thesub-systems 110, 120, 140 in a more proactive and flexible manner.

As mentioned before, as long as the sub-systems 110, 120 140 areoperating under static conditions the sum of the powers added to andsubtracted from the summation point 150 are equal to zero. In otherwords, under static conditions we have:

Pload+Pt+Ph=0  (8)

If the sub-systems 110, 120, 140 are connected to a summation point 150representing a flywheel which causes the sub-systems to operate at thesame rotational speed we have:

Tload+Tt+Th=0  (9)

Now, if the predicted load (Pload,pred=Pt,pred+Ph.pred) on thecombustion engine 120 exceeds the power Pe.pred predicted to beavailable from the engine 120 we will have a situation wherein the sumof the powers in the summation point 150 is below zero, which can berepresented by the following relation:

Pe.pred+Pt.pred+Ph.pred<0  (10)

If the sub-systems 110, 120, 140 are connected to a summation point 150representing a flywheel which causes the sub-systems to operate at thesame rotational speed we have:

Te.pred+Tt,pred+Th.pred<0  (11)

As previously described:

-   Te is the torque currently available from the combustion engine 120,-   Tload is the fraction of Te that is currently provided by the    combustion engine 120,-   Th is the torque currently required by the working hydraulic system    140,-   Tt is the torque currently required by the transmission line 110,-   Pe is the power currently available from the combustion engine 120,-   Pload is the fraction of Pe that is currently provided by the    combustion engine 120,-   Ph is the power currently required by the working hydraulic system    140,-   Pt is the power currently required by the transmission line 110,-   Te.pred is the torque predicted to be available from the combustion    engine 120,-   Th,pred is the torque predicted to be required by the working    hydraulic system 140,-   Tt.pred is the torque predicted to be required by the transmission    line 110,

Pe.pred is the power predicted to be available from the combustionengine 120,

-   Ph.pred is the power predicted to be required by the working    hydraulic system 140,-   Pt.pred is the power predicted to be required by the transmission    line 110,

In a situation where the predicted load (Poad,pred=Pt.pred+Ph,pred) onthe combustion engine 120 exceeds the power Pe.pred predicted to beavailable from the combustion engine 120, as illustrated by therelations 10 and 11 above, we will receive a reduced rotational speed nefor the combustion engine 120 and there is a clear risk of overloadingand potentially stalling the engine 120. Naturally, the same is validmutatis mutandis for the predicted torgt/es Te,pred. Tt,pred andTh,pred.

To remedy the risk of overloading and potentially stalling the engine120 it is preferred that the rotational speed ne for the combustionengine 120 is increased as soon as it is detected that a predicted load(Pt.pred+Ph.pred) on the combustion engine 120 will exceed the predictedpower (Pe.pred) that will be available from the engine 120. This cane.g. be achieved by the torque-control unit 200 transmitting a messagevia a CAN-bus to an engine ECU or similar unit for controlling thecombustion engine 120 in the wheel loader 1 so as to increase therotational speed of the engine 120.

However, it is more preferred that the rotational speed ne for thecombustion engine 120 is increased as soon as it is detected that apredicted load increase on the combustion engine 120 will exceed orbecome equal to the current load margin Pdiff=Pe - Pload. which has beendiscussed above with reference to FIG. 5.

This can e.g. be expressed by the following relation:

(Pt.pred+Ph.pred)−(Pt+Ph)≧Pdiff  (11)

It is even more preferred that the rotational speed ne for thecombustion engine 120 is increased as soon as it is detected that thepredicted load increase on the combustion engine 120 will exceed apercentage of the current load margin Pdiff, e.g. a percentage in theinterval of about 50%-90% of the current load margin Pdiff. This is toensure that there is still a sufficient margin for an additionalincrease of the load on the combustion engine 120 caused by othersystems within the wheel loader 1.

However, to avoid conflicts with increasingly harder emissionregulations, particularly with respect to exhaustion gases and visiblesmoke emanating from the combustion engine 120 in response to anincrease of the load on the engine 120, it is preferred that therotational speed ne for the engine 120 is increased in a controlledmanner when responding to an increased load. In particular it ispreferred that the rotational speed ne is increased to the requiredlevel over a period that can be extended if necessary.

A controlled increase of the rotational speed ne for the combustionengine 120 in the exemplifying wheel loader 1 can e.g. be accomplishedby temporarily decreasing the displacement Dp for the pumps 142, 144,148 in the working hydraulic system 140. The displacement Dp can e.g.directly be adjusted by means of electric step motors, hydraulic pistonsor similar, or indirectly e.g. by hydraulic valves that are arranged toreduce the load-sensing signal flow of hydraulic fluid to the pumps 142,144, 148.

This creates a temporary reduction of the power required by the pumps142, 144, 148 in the hydraulic system 140 and hence a temporaryreduction of the power required by the combustion engine 120. Thecombustion engine 120 is hereby given an extended period to reach therequired rotational speed.

Additional Embodiments

An Auxiliary Power Source

Accomplishing a controlled increase of the rotational speed for thecombustion engine 120 by temporarily decreasing the displacement Dp forthe pumps 142, 144, 148 in the working hydraulic system 140 as suggestedabove suffers from the drawback that an operator of the wheel loader 1will experience a hydraulic system 140 with a reduced performance.

Hence, in another embodiment of the invention a controlled increase ofthe rotational speed ne for the combustion engine 120 is achieved bycreating an extended period for the engine 120 to reach the requiredrotational speed by utilizing an auxiliary power source in the form ofan electric machine 112. This avoids the drawbacks of having to reducethe performance of the any of the sub-systems 110, 120, 140 as will beclear from the description below.

FIG. 6 shows the transmission line 110 provided with at least oneelectric machine 112. The electric machine 112 is arranged tooperatively add torque to the transmission line 110 in a suitableposition downstream the combustion engine 120. Preferably the electricmachine 112 is arranged in a position between the internal combustionengine 120 and the transmission unit 114. The electric machine 112should be able to operate in at least one quadrant, i.e. as motor in atleast one direction of rotation. The electric machine 112 is coupled tothe transmission line 110 so that torque can be exchanged between thetransmission line 110 and the electric machine 112. This can be achievedby a plurality of means and functions which are well known to thoseskilled in the art, e.g. by a mechanic coupling of one or several shaftsin the transmission line 110 to the output shaft of the electric machine112.

FIG. 7 is a schematic block diagram which schematically illustrates thepower exchange between the units of a wheel loader as illustrated inFIG. 6.

It is preferred that the electric machine 112 is connected to thetorque-control unit 200 being arranged to operatively control the torqueexchanged between the transmission line 110 and the electric machine112. The torque-control unit 200 is preferably arranged to operativelyprovide the machine 112 with electric power from an electric powersource 210. This enables the torque-control unit 200 to operate theelectric machine 112 as a motor which adds torque to the transmissionline 110 for reducing the load on the combustion engine 120.

The electric power source 210 can be designed in many different ways, aslong as it is able to provide electricity to the electric machine 112.One alternative is to use a generator powered by a separate combustionengine or similar. However, it is more preferred to use a battery or asuper capacitor or even fuel cells and similar alternatives that operatewithout any separate combustion engine or similar. Here it should beadded that the electric machine 112 can be arranged to work as agenerator for charging the electric power source 210 when the generalload on the combustion engine so permits. Naturally, the chargingfunction of the electric machine 112 is provided in addition to theother functions described herein.

In one embodiment of the invention the electric machine 112 is operatedby the torque-control unit 200 to add a predetermined amount of torqueto the transmission line 110 to reduce the load on the combustion engine120. The predetermined amount may e.g. be the maximum power of theelectric machine 112 or a predetermined fraction of that power. This issimilar or equal to an all-or-nothing function or an on/off function.The simplicity of this function is a clear advantage. However, adrawback is that the added amount of torque has no significantcorrelation with the load on the combustion engine 120. Hence, the addedamount of torque may be too small or too large. A small amount may givean insufficient support for the combustion engine 120. A large amountmay disturb other functions in the wheel loader 1. Hence, in anotherembodiment of the invention it is preferred that the electric machine112 is operated by the torque-controi unit 200 to add an amount oftorque to the transmission line 110 so that the predicted increase ofthe load on the combustion engine 120 will be neutralized or at leastsubstantially neutralized. This can be accomplished by adding an amountof power that equals or correspond to the predicted increase of the loadon the engine 120. In one embodiment this is achieved by adding anamount of power that equals or correspond to the first time derivativeof the load on the engine 120. Alternatively, this may be accomplishedby adding an amount of power that equals or correspond to the rate ofthe increase of the load on the engine 120. In one embodiment this isachieved by adding an amount of power that equals or correspond to thesecond time derivative of the load on the engine 120.

However, the amount of torque that is added to the transmission line 110by the electric machine 112 in the embodiments described above is basedon a value that is essentially depending on the increase of the load onthe combustion engine 120. In other words, the added torque has nosignificant correlation with the current working point of the combustionengine 120.

Hence, given a current working point for the combustion engine 120 at arotational speed of x (rpm) providing an available output torque of x(Nm) and an available output power

Pe from the combustion engine 120, as discussed above with reference toFIG. 5. Then the amount of torque added to the transmission line 110should be of such an amount so that the predicted increase of the loadon the combustion engine 120 is not exceeding the current load marginPdjff. Alternatively, the amount of torque added to the transmissionline 110 should be of such an amount so that the predicted increase ofthe load on the engine 120 does not exceed a predetermined percentage ofthe current load margin Pdjff, e.g. a percentage in the interval ofabout 50%-80% of the current load margin Pdiff.

In addition, the torque-control unit 200 is preferably arranged toreduce the amount of torque that is added to the transmission line 110by the electric machine 112 when the rotational speed of the combustionengine 120 is increased in a controlled manner to meet the predictedincrease of the load on the engine 120, since an increased rotationalspeed for the engine 120 leads to an increased margin with respect toengine overload and possible stall etc. Further Ilydraulic Features andAlternative Implements

Although the exemplifying hydraulic system 140 illustrated in FIG. 2-3has three hydraulic pumps 142, 144, 146 other embodiments may have one,two, four or more hydraulic pumps. In a preferred embodiment of theinvention the working machine has at least two implement and/or steeringfunctions, and at least one said hydraulic pump is arranged for eachimplement and/or steering function.

As described in connection to the FIG. 1, the working machine 1 can havean implement 2 in the form of a bucket 3 which is operated by means ofthe hydraulic system 140. However, it should be emphasised that otherimplements are usable. When applying the invention on a working machinesuch as an articulated hauler or a truck, the implement can instead befor example a dump body. Usually a hydraulic pump and working cylindersare used for the operation of the dump body during the dumping movement.

It is to be understood that the present invention is not limited to theembodiments described above and illustrated in the drawings; rather, theskilled person will recognize that many changes and modifications may bemade within the scope of the appended claims.

1. A method for operating a working machine provided with: a powersource providing power and a plurality of power consuming systemsconnected to the power source, comprising providing a model predicting apower demanded by at least one of the power consuming systems, detectingat least one operational parameter indicative of a power demand, usingthe detected operational parameter in the prediction model, andbalancing a provided power to the demanded power according to theprediction model.
 2. A method according to claim 1, comprising balancinga provided power to the demanded power so that a load on the powersource is reduced.
 3. A method according to claim 1, comprisingdetecting at least one operational parameter indicative of a currentworking condition of the power source and/or at least one of the powerconsuming systems.
 4. A method according to claim 3, comprisingdetecting at least one operational parameter indicative of a currentworking condition by measuring a rotational speed and measuring orestimating a torque.
 5. A method according to claim 3, comprisingdetecting at least one operational parameter indicative of a currentworking condition by measuring a hydraulic pressure and measuring orestimating a flow provided by a hydraulic pump in one of the powerconsuming systems.
 6. A method according to claim 1, comprisingdetecting at least one operational parameter by detecting at least oneinput command from a working machine operator.
 7. A method according toclaim 1, wherein the power consuming systems are connected to the powersource via a branching-off portion, and that the prediction modelcomprises a power summation point, which represents the branching offportion.
 8. A method according to claim 7, comprising balancing thepower when the prediction model indicates that the power communicatedbetween the power source and the power consuming systems is or will bebelow zero in the summation point.
 9. A method according to claim 8,comprising temporarily adjusting the balance until the prediction modelindicates a balance condition in which the power is zero or above zeroin the summation point.
 10. A method according to claim 1, wherein thethe prediction model is adapted to predict a total power demanded by allof the power consuming systems.
 11. A method according to claim 1,wherein the prediction model is adapted to predict an individual powerdemand of each of the power consuming system.
 12. A method according toclaim 1, wherein the the prediction model comprises a first portion,which is characteristic of a behaviour of the power source.
 13. A methodaccording to claim 1, wherein the prediction model comprises a secondportion, which is characteristic of a behaviour of a first of the powerconsuming systems.
 14. A method according to claim 1, wherein the theprediction model comprises a third portion, which is characteristic of abehaviour of a second of the power consuming systems.
 15. A methodaccording to claim 1, comprising balancing the provided power to thedemanded power by adding torque by means of an external power source.16. A method according to claim 1, comprising balancing the providedpower to the demanded power by adding torque by means of at least oneelectric machine.
 17. A method according to claim 15, comprising addingthe torque to a first of the power consuming systems.
 18. A methodaccording to claim 1, comprising balancing the provided power to thedemanded power by effecting the power source and/or at least one of thepower consuming systems in case an adjustment with regard to power isdetermined to be needed.
 19. A method according to claim 1, comprisingbalancing the power by reducing an actual power provided to at least oneof the power consuming systems relative to a demanded power.
 20. Amethod according to claim 1, comprising balancing the power by scalingdown an actual power provided to at least one of the power consumingsystems relative to a demanded power.
 21. A method according to claim 1,comprising simultaneously monitoring a demanded power of a plurality ofthe power consuming systems and correspondingly balancing the power. 22.A method according to claim 1, wherein the power consuming systemscomprises a working hydraulic system comprising at least one hydraulicpump powered by the power source for moving an implement on the workingmachine and/or for steering the working machine.
 23. A method accordingto claim 22, comprising adjusting the power balance by temporarilydecreasing the displacement (Dp) for at least one of the pumps arrangedin the working hydraulic system.
 24. A method according to claim 22,comprising adjusting the power balance by effecting at least onehydraulic valve arranged in the working hydraulic system.
 25. A methodaccording to claim 1, wherein the power consuming systems comprises atransmission line arranged between the power source and driving wheelsof the working machine for transmitting torque from the power source tothe driving wheels.
 26. A method according to claim 16, wherein thepower consuming systems comprises a transmission line arranged betweenthe power source and driving wheels of the working machine fortransmitting torque from the power source to the driving wheels, themethod comprising using the electric machine arranged upstream atransmission unit arranged in the transmission line, or upstream agearbox arranged in the transmission line.
 27. A method according toclaim 26, wherein the power consuming systems comprises a workinghydraulic system comprising at least one hydraulic pump powered by thepower sourcefor moving an implement on the working machine and/or forsteering the working machine, and wherein the power source ismechanically connected to the transmission line and the workinghydraulic system.
 28. A method according to claim 7, wherein the powerconsuming systems are connected to the power source via a branching-offportion, and that the prediction model comprises a power summationpoint, which represents the branching off portion wherein thebranching-off portion is defined by a fly wheel arranged on an outputshaft of the power source.
 29. A method according to claim 25,comprising adjusting the power balance by effecting a controllablegearbox in the transmission line.
 30. A method according to claim 1,wherein the power source is an internal combustion engine.
 31. A methodaccording to claim 1, wherein the operated working machine is a wheelloader.
 32. A working machine provided with: a power source adapted toprovide power and a plurality of power consuming systems connected tothe power source, comprising: a control unit which is adapted to predicta power demanded by at least one of the power consuming systems on thebasis of at least one operational parameter indicative of a powerdemand, means for detecting the at least one operational parameter,wherein the detection means is connected to the control unit, and meansfor balancing a provided power to the demanded power according to theprediction model, wherein the balancing means is connected to thecontrol unit.
 33. A working machine according to claim 32, wherein thedetection means is adapted to detect at least one operational parameterindicative of a current working condition of the power source and/or atleast one of the power consuming systems.
 34. A working machineaccording to claim 33, wherein the detection means is adapted to detectat least one operational parameter indicative of a current workingcondition by measuring a rotational speed and measuring or estimating atorque.
 35. A working machine according to claim 33, wherein thedetection means is adapted to detect at least one operational parameterindicative of a current working condition by measuring a hydraulicpressure and measuring or estimating a flow provided by a hydraulic pumpin one of the power consuming systems.
 36. A working machine accordingto claim 32, wherein the detection means is adapted to detect least oneoperational parameter by detecting at least one input command from aworking machine operator.
 37. A working machine according to claim 32,wherein the power consuming systems are connected to the power sourcevia a branching-off portion.
 38. A working machine according to claim32, wherein an external power source is adapted for providing power byadding torque.
 39. A working machine according to claim 32, wherein atleast one electric machine is adapted for providing power by addingtorque.
 40. A working machine according to claim 32, wherein the meansfor power balancing is adapted to effect the power source and/or atleast one of the power consuming systems.
 41. A working machineaccording to claim 32, wherein the power consuming systems comprises aworking hydraulic system comprising at least one hydraulic pump poweredby the power source for moving an implement on the working machineand/or for steering the working machine.
 42. A working machine accordingto claim 41, wherein the means for power balancing is adapted totemporarily decreasing the displacement (Dp) for at least one of thepumps arranged in the working hydraulic system.
 43. A working machineaccording to claim 41, wherein the means for power balancing is adaptedto effect at least one hydraulic valve arranged in the working hydraulicsystem.
 44. A working machine according to claim 32, wherein the powerconsuming systems comprises a transmission line arranged between thepower source and driving wheels of the working machine for transmittingtorque from the power source to the driving wheels.
 45. A workingmachine according to claim 44, wherein at least one electric machine isadapted for providing power by adding torque, and wherein the electricmachine is arranged upstream a transmission unit arranged in thetransmission line, or upstream a gearbox arranged in the transmissionline.
 46. A working machine according to claims 40 and 43, wherein thepower consuming systems comprises a working hydraulic system comprisingat least one hydraulic pump powered by the power source for moving animplement on the working machine and/or for steering the workingmachine, and the means for power balancing is adapted to effect at leastone hydraulic valve arranged in the working hydraulic system, andwherein the power source is mechanically connected to the transmissionline and the working hydraulic system.
 47. A working machine accordingto claim 36, wherein the branching-off portion is defined by a fly wheelarranged on an output shaft of the power source.
 48. A working machineaccording to claim 32, wherein the power source is an internalcombustion engine.
 49. A working machine according to claim 32, whereinworking machine is a wheel loader.